Off the set, M. M. holds a horse bit in her mouth waiting for the session to begin (#1).  She seems lost in thought.  Is she contemplating the metal bit as she looks up at the camera (#2)? 
   Now, in front of the seamless, M. M. stands with her back arched, horse bit in her mouth (#3), her arms up and hands to the side of her mouth (#4).  She moves her hands down to her ankles (#5). After she takes the bit out I shoot a close up of her face showing the spittle marks left by the metal restraint on sides of her mouth (#6).  I suggest you zoom in to see the wetness better.